1. Field of Invention
The present invention relates generally to the field of cleaning equipment used in oilfield operations, and more specifically to methods and apparatus for cleaning screens used in solid/liquid separations in oilfield operations.
2. Related Art
The need for solids control, such as in conjunction with the use of drilling mud during hydrocarbons well drilling, has long been known. Drilling mud, typically a mixture of clay and water and various additives, is pumped through a hollow drill string (pipe, drill collars, bit etc.) down into the well and ejected through holes in the drill bit. Among other functions the mud picks up cuttings, rock and other solids from the bottom of the well and carries these solids away from the bit upward and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is directed to the shale shaker, a device consisting essentially of a series of screens which catch and remove solids from the mud as the mud passes through the screens. Each screen is caused to vibrate by vibrating equipment (shale shakers), in such a manner as to create a longitudinal flow of trapped solids in either direction on the top surface of the screen for removal and disposal of the solids. This filtering, along with other cleaning processes allows the mud to be reused.
The fineness or coarseness (mesh size of the mesh of a screen may vary depending on such factors as flow rate and size of solids to be separated by the screen. During this process the openings in the screen mesh tend to plug or solids get trapped and the fluid components of the mud are restricted from passing through the screen, reducing the flow capacity of the screen.
Once solids are separated by the screens in the shale shaker, in accordance with the prior art, upon completion of drilling the well the screens are taken off of the shale shaker, washed and cleaned in an open environment, and prepared to be used on the next well, or the screens are discarded if there was damage to the screen mesh during prior drilling operations. A typical practice is to simply lean the screens against a railing or other support on a drilling rig or work-over rig and hydroblast the screens, perhaps with some cleaning agent, with the excess water and cleaning agent simply draining into the local environment. As will be noted, this practice may allow contaminants and potentially hazardous materials to enter the environment. In addition, since the water and cleaning agent are not recycled, the volume of water and any cleaning agent used is quite voluminous and undesirable.
It would be advantageous and an advance in the art of cleaning drill cuttings screens to eliminate or substantially reduce the amount of contaminants and potentially hazardous materials entering the environment during cleaning of such screens, and to reduce the amount of water and other cleaning agents used.